Conventionally, various electronic devices which perform predetermined function in response to an operation of the user are known in the technical field. For example, an electronic device inputs an operation signal from an input device which includes a plurality of operational keys, and performs one of functions according to the operation input from the user. Alternatively, an electronic device may include a graphical user interface device which includes a display device for displaying an operation screen image and a pointing device for inputting an operation signal. In this case, the electronic device performs one of functions according to the operation input of the user inputted based on the operation screen image.
A touch panel is known as an input device. The touch panel detects a touching motion of a user and locates a position of the touching motion on the touch surface. Then, touch panel inputs the operation signal which is coordinates of the position of the touching motion. Generally, the touch panel includes a transparent sheet and is disposed on a display screen of a display device.
In addition, the following patent document 1 discloses an input device using a touch panel. In this device, the device identifies a user who touches the touch panel. The device applies an electric signal on a contact surface to the user and detects a touching operation by the electric signal which flows through a user's body when the user touches the contact surface.
In addition, the following patent document 2 discloses an electronic device for drawing which has a display device with a touch panel. The device includes color selection keys. If one of the color selection keys is touched, the device enables the user to use the color corresponding to touched color selection key. Then, the electronic device controls a display device to display a drawing by using an enabled color for the user. The drawing is drawn with a user's finger on a drawing area defined on the touch panel.